R/ddplot.R

In musto101/wilcox_R: What the package does (short line)

ddplot <-
function(x)
{
# Makes a DD plot. cov.mcd is used for the RDi.
# Click left mouse button to identify points.
# Click right mouse button to end the function.
# Unix systems turn on graphics device eg enter
#  command "X11()" or "motif()" before using.
# R users need to type "library(lqs)" before using.
	p <- dim(x)[2]
	center <- apply(x, 2, mean)
	cov <- var(x)
	md2 <- mahalanobis(x, center, cov)
	out <- cov.mcd(x)	# or use out <- cov.mve(x)
	center <- out$center
	cov <- out$cov
	rd2 <- mahalanobis(x, center, cov)	
	# md is the classical and rd the robust distance
	MD <- sqrt(md2)
	rd <- sqrt(rd2)	
	#Scale the RD so the plot follows the 0-1 line
#if the data is multivariate normal.
	const <- sqrt(qchisq(0.5, p))/median(rd)
	RD <- const * rd
	plot(MD, RD)
	abline(0, 1)
	identify(MD, RD)	#  list(MD = MD, RD = RD)
}